1. Field of the Invention
The present invention relates to an information recording apparatus as represented by a floppy disk drive apparatus and the like.
2. Description of the Prior Art
Here, as an example of a conventional information recording apparatus, a floppy disk drive apparatus (hereinafter referred to as an “FDD apparatus”) will be described. An FDD apparatus is an information recording/reproducing apparatus for writing data to and reading data from a floppy disk (hereinafter referred to as a “disk”) having a plurality of concentrically arranged tracks.
The FDD apparatus receives a write gate signal from a host (such as a personal computer) to permit or inhibit write operation against the disk. When write operation is permitted, the write gate signal is made active (for example, turned to L level). However, write operation against the disk is permitted not by the write gate signal being made active alone. In general, the write gate signal is regarded as valid only when the host has selected the FDD apparatus (a drive select signal is active), a spindle motor has started rotating the disk (a motor on signal or ready signal is active), and a write disable switch on the disk is released (a write protect signal is active).
In the conventional FDD apparatus configured as described above, the write gate signal is not regarded as valid until write operation against the disk becomes possible. Thus, it is true that no unnecessary write operation is performed in that period.
However, this control of write operation assumes that the interface signals fed from the host are normal. In other words, if the interface signals are abnormal (for example, all the interface signals are active simultaneously), as because of instantaneous interruption of the supply of power to the FDD apparatus and the host, or because of transient response accompanying the turning on and off of the supply of power resulting from the FDD apparatus using a different power supply line from the floppy disk controller provided in the host, or because of failure of the interface circuit provided in the FDD apparatus, the aforementioned conditions for validating the write gate signal are fulfilled unexpectedly, and therefore there is a risk of erroneous write operation being performed against the disk.